Rotary pump



Dec. 8, 1959 L. CRANDALL 2,915,982

ROTARY PUMP I Filed Feb. 14, 1955 2 Sheets-Sheet 2 76, 77 59 INVENTOR.

Lam 0644 0444 Jay/(42? ArroeA/EV.

United States Patent ROTARY PUMP Loid Crandall, Alhambra, Calif.

Application February 14, 1955, Serial No. 487,907

13 Claims. (Cl. 103-126) This invention relates generally to a rotary pump construction and more particularly, to a rotor gear pump for high pressure, high viscosity fluids and provided with novel means responsive to pressure of fluid which has been pumped to seal end faces of relatively rotatable rotors in said pump.

Gear pumps may include an inner gear provided with external teeth and an outer gear provided with internal teeth, the two gears being eccentrically mounted and the number of teeth on the inner gear being less than those on the outer gear. End plates are usually provided in fixed relation to the gears and with a very close tolerance. Operation of such prior gear pumps results in frictional wear of one or both of the surfaces of the end plates whereby leakage of fluid occurs along the end plates from between the enmeshed teeth with the result that the gear pump is unable to maintain a desired pressure of fluid in the discharge side of the pump. Such end plate leakage usually does not become critical in low pressure gear pumps or gear pumps used for low viscosity fluids.

However, there is a present need in industry, particularly automotive and aircraft industry, for a gear pump which is capable of pumping high viscosity fluids such as high octane gasoline, hydrogen peroxide and various other highly volatile fluids of high viscosity under pressures extending above 1,500 pounds per square inch. Prior gear pump constructions have been unable to satisfactorily meet such a requirement because of the loss of pressure due to end plate leakage.

This invention contemplates a novel rotary pump construction which substantially eliminates end plate leakage under high pressure and which is capable of efliciently pumping high viscosity and'high volatile fluids. The invention contemplates a novel construction of sealing means for end faces of rotary pump assembly wherein said sealing means is responsive to pressure of fluid being pumped. The novel construction of this invention also contemplates a sealing means for such a rotary pump assembly wherein minimum tolerance is achieved between end faces of the gear rotor members so that leakage under high pressure is substantially eliminated.

It is, therefore, a primary object of thisinvention to disclose and provide a novel rotary pump construction for use in pumping high viscosity fluids under high pressure.

An object of this invention is to disclose a rotary pump wherein novel end plate sealing means are rotatable with and in the same direction as relatively rotatable inner and outer rotor members.

Another object of this invention is to disclose and provide a rotary pump wherein pressure-responsive thrust plate members are slidably mounted on the pump shaft and wherein means are provided for urging in sealing relation said members against end faces of the rotor pump assembly.

A' still further object of this invention is to disclose and provide a novel pump construction employing pres- 2,915,982 Patented Dec. 8, 1959 sure-responsive thrust plates for end sealing means against a rotor assembly wherein wear is reduced to a minimum and substantially eliminated.

The invention contemplates a rotary pump construction wherein inner and outer relatively rotatable rotors and slidable end thrust plates for said rotors are rotatable in the same direction as said rotors and urged against end faces of said rotors and towards annular edge faces of a stationary bearing sleeve means in running engage ment therewith.

A further object of this invention is to disclose a rotary pump construction as described above wherein means are provided for limiting fluid under pressure to selected outboard areas of said pressure responsive thrust plate members.

Generally speaking, this invention contemplates a rotary pump provided with a housing having a chamber with inlet and outlet ports thereto. A rotor assembly is mounted within said chamber and includes a shaft carrying an inner rotor, a bearing sleeve mounted in said housing and provided with an internal, cylindrical surface eccentric to the axis of said shaft, said sleeve being provided with inlet and outlet slots in communication with said ports. An outer rotor is rotatably mounted in said bearing sleeve in meshed relation with said inner rotor and is provided with openings in communication with said slots. Means for sealing the end faces of said rotors comprises disc-like thrust plates slidably mounted on said shaft and extending over the end faces of said rotors into close running clearance with end faces on said bearing sleeve. Passageway means are provided for communication between the discharge side of the chamber and the outboard faces of said thrust plates whereby pumped fluid under pressure urges said thrust plates into sealing engagement with said rotors and with said bearing sleeve, said thrust plates being rotatable in the same direction as said rotors.

Other objects and advantages of this invention will be readily apparent from the following description and the drawings.

'In the drawings:

Fig. l is a sectional view of a rotary pump embodying this invention, the section being taken in a longitudinal plane passing through the axis of the pump.

Fig. 2 is a transverse sectional view taken in the plane indicated by line IIII of Fig. l.

Fig. 3 is a fragmentary sectional view taken in the plane indicated by line III-III of Fig. 2, the rotor assembly within the housing being shown in elevation.

Fig. 4 is a sectional'view of a rotary pump embodying a modification of this invention, the section being takenin a longitudinal plane passing through the'axis of the pump.

Fig. 5 is an enlarged fragmentary sectional view taken in the same plane as Fig. 4.

Fig. 6 is a fragmentary perspective view of a bearing sleeve means employed with the rotary pump of this invention.

In the exemplary embodiment of this invention shown in Figs. 1-3 inclusive, a rotary pump generally indicated at 10 may comprise a pump casing orhousing 11 which includes an open-ended cylindrical hollow housing member 12 having oppositely directed, diametrically opposed enlarged external boss-like portions 13. The housing member 12 includes, in said portions 13, inlet and outlet ports' 14 and 15 respectively which may be internally threaded to provide a suitable connection to pipe or conduit 16 for fluid. It is understood other means for connecting conduit 16 to the housing maybe employed. 7

The cylindrical housing member 12 may be supported between spaced, opposed housing end plates 18am! 19,

. planar face and an inner peripheral recess 21 defining an annular shoulder 22 which may be received within an open end of the housing member '12. Each shoulder 22 may carry suitable seal means 23. The end plates 18 and 19 and the housing member 12 may be secured together by suitable circumferentially spaced through bolts 24; said bolts may have threaded engagement at 25 with end plate 19. It is understood that other suitable means may be provided for securing together end plates 18 and 1 9and housing member 12.

The housing 11 thusdefines an internal chamber 27 of generally cylindrical form and in communication with inlet and outlet ports 14 and 15.-

,Within internal chamber 27 is provided a rotor assembly generally indicated at 28, said rotor assembly being assembled as aunit'and introduced intosaid chamber before securing end plate 19. The rotor assembly 28 includes a rotatable drive shaft 29 which may be mounted in bearing means 30 carried by end plates 18 and 19. As illustrated the bearing means 30 may comprise a sleeve bearing of any suitable bearing material. It is understood thatflother bearing means may be used.

It will be noted that end plate 18 supports bearing 30 in an axial bore 31 which does not extend through end plate 18 and that the end of shaft 29 and bearing 30 are spaced from the bottom wall of the bore 31. End plate 19 may be provided with an enlarged recess 32, coaxial with an axial through bore 33 in which bearing means 30 are mounted, in order to mount a suitable shaft sealing means generally indicated at 34. While the construction of the shaft sealing means 34 is shown in detail, it is not described because it does not form part of this invention and any suitable shaft sealing means may be employed. 7

The shaft 29 carries an inner rotor 36 whichmay be keyed thereto in well known manner for rotation therewith. The inner rotor 36 is provided with a selected number of external teeth 37 of a selected conf guration.

An outer rotor 38 is provided with internal teeth 39 in number one morethan the number of teeth, on the inner rotor. The configuration of the teeth on the outer rotor is substantially complementary to the configuration of the teeth on the inner rotor so thatan internal tooth 39 will be received within a tooth space 40 between teeth 37 on the inner rotor in substantially complementary relation and a tooth 37 on the inner rotor will be similarly received within a tooth space 41 provided on the outer rotor, The, outer rotoris provided with a plurality of spaced through openings 42 having communicat ion with tooth spaces 41 and extending to outer cylin-,

drical surface 43 of the outer rotor.

The outer rotor 38 is eccentrically mounted with respect to innerrotor 36 so that chambers of variable volume are provided between enmeshed teeth 'of the inner and outer rotors as the rotors rotate relative to each other. The faces of said teeth are so configured that when the rotors are eccentrically mounted opposed teeth are in line contact along opposed surfaces so that said chambers are virtually sealed one from the other.

- In. one position of the teeth a chamber of minimum cylindrical internal surface 45 for rotatably mounting therewithin the outer'rotorj38; The sleeve means 44 includes an elongatedintake slot 46.extending centrally between end facesAT of the sleeve means 44 and'in. c9m-, munication with'inlet port '14; The slot 46 may subtend an angle of slightly less than 180 and is aligned with and in communication with openings 42 provided in outer rotor 38. On the opposite side of the bearing sleeve means 44 is provided an outlet slot 49 which is also in alignment with and in communication with open ings 42 in the outer rotor and with outlet port 15, the slot 49 also subtending an angle of slightly less than There is thus provided on the internal surface of the sleeve means top and bottom'bearing surfaces 50 and 51 which provide partitions between said intake and out let slots in the bearing sleeve means.

Outlet slot 49 may be slightly greater in width, or in area of opening, so that a hydraulic balance may be achieved between fluid pressure on'the discharge side of the pump chamber and the internal pump pressure so as to substantially hydraulically balance the outer rotor 36.

It may be noted that at this point that the widths of the inner rotor, outer rotor and bearing sleeve means are substantially! equal so that .end faces 47 of the sleeve means 44, end faces 52 of the outer rotor 38, and end faces 53 of the inner rotor 36'lie in substantially parallel planes.

Means for sealing the variable volume chambers provided between the inner and outer. rotors to prevent leakage therefrom may comprise a pair of circular axially ported end thrust plates 55, each slidably mounted as at 56 on shaft 29. Each thrust plate 55 is provided with an inboard surface .57 which extends over end faces 52 and 53 of the outer and inner rotors and marginalQcircumferential portions of edge faces 47 on the bearing sleeve means 44. The outboard face 58 of each thrust plate 55 is spaced from the internal faces 20 of the housing end plates 18 and 19. Each end thrust plate 55 may be initially biased into sealing engagement with said end faces 47, 52, 53 by a spring ring 59 carried by shaft 29.

The springrings 59, which bias the thrust end plates inwardly against'the inner and outer rotors toward bearing sleeve means also serve to hold said pump in assembly as a unit prior to fitting within the internal chamber 27. Passageway means may be provided in the bearing sleeve means 44 for communication between outlet port 15 and the spaces between the internal faces 20 on housing and plate members 18 and 19 and the outboard faces of the thrust end plates 55. In this example, such passageway means may comprise a bore 61 drilled through the bearing sleeve means at a point intermediate the ends of outlet slot 49'and radially outwardly .of the circumferential edge of the thrust end plates .55. It will be readily apparent thatthe'bore 61 thus provides for fluid under pressure from theoutlet side of the pump to act upon the thrust end plates so that they are urged invwardly into sealing engagement with the bearing sleeve means in direct response to variations in pressure of fluid being p mped. v e In operation of the rotary'purnp described above, it will be understood that the drive shaft 29 maybe rotatably driven by any suitable power means such as an electrical motor. Shaft 29 rotates inner rotor 36 which in turn causesrelative rotation of outer rotor 38. Relative rotation between the inner and outer rotor causes the chambers between the interengaging teeth to vary in volume because of the eccentric mounting of the rotors. Fluid is drawn through inlet port 14, through intake slot 46 and openings 42 into the expanding chambers on the inlet side of the pump assembly. on theoutlet side, the chambers between the enmeshed teeth are contracting and fluid is pumped therefrom through openings 42 in the outer rotor and through outlet slot 49 to the outlet port. The discharged fluid under pressure circulates through passagewaymeans 61 into the spaces in chamber .27between the thrust end plates and the housing end inwardly into tight sealingengagement with theend faces of the rotors 36 and 38.

It should be particularly noted that the end thrust plates 55 may rotate either with the inner rotor 36 or with the outer rotor 38 depending upon contact made thereby with one or the other rotor. The .end thrust plates will rotate with one or the other rotor and thus will rotate relative to the other rotor at a relatively small differential in rotative speed. A condition producing wear on sealing thrust plates is thus reduced to a minimum.

Normally the width of the bearing sleeve means may be slightly less by a running clearance fit than the width of the inner and outer rotors. Thus, the outer circumferential, marginal inner surface portions .of the thrust end plates may initially contact end faces 52 and 53 of the rotors. As the thrust plates are. rotated by oneor the other of said rotors and are urged against end faces 52, 53 by fluid under pressure, it will be apparent that wear between the end thrust plates and end faces 52, 53 amounts to only a wearing-in of the contacting surfaces. As a result, minimum tolerance is achieved between the end faces of the rotors and the end thrust plates and such tolerance does not tend to increase with continued operation of the rotary pump because of the pressure fluid. End play of the pump rotors, bearing sleeve means and thrust plates relative to each other is substantially eliminated and any axial movement or displacement of the pump assembly does not affect the end thrust plate seal. There is, therefore, afforded a seal means which substantially eliminates end plate-leakage in a rotary pump assembly and which is responsive to fluctuations in fluid pressure. As a further result, the gear pump means of this invention is capable of pumping'high viscosity, highly volatile fluids at relatively high pressures.

In the modification shown in Figs. 4 and 5, the rotary pump is constructed similarly to that described above with the exception that annular seal means generally indicated at 65 are carried by housing end plates 18 and 19' for limiting the area of fluid pressure contact with end thrust plates 55'. Such a construction may be desirable when a different type of bearing means supporting the drive shaft 29 is employed and where application of pressure fluid is desired more directly against rotor end faces 52, 53.

Housing 11' and rotor assembly 28 are constructed the same as that previously described. Each housing end plate 18' and 19' may be provided with an annular recess 66 of a selected radius in internal faces 20. Within each recess 66may be provided a biased seal means 65 which is of well-known construction and which may comprise an annular outer casing 67 within which is carried an O-ring 68 and a retaining ring 69. Inwardly of the O-ring is a fluid pressure-responsive sleeve 70 which isnormally biased outwardly by an annular spring ring 71 which bears against an edge of pressure.sleeve,70 and a wall of casing 67. The sleeve 70 is slidably mounted on an internal sleeve bearing 72 which supports at its outer edge an annular wear member 73 of suitable bearing material, said Wear member 73 being received within a recess 74 provided on sleeve 70. Fluid under pressure which enters the casing will exert pressure against annular pressure face 75 of sleeve 70 to urge the wear member 73 outwardly and against the opposed outboard surface of the end thrust plate 55. Fluid under pressure in the space between the internal face 20' of the end plates and the outboard faces of the end thrust plates 55 will thus not only serve to seal the end faces of the rotor assembly but will also serve to urge the bearing member 73 against the outboard face of the end thrust plate 55'. Thus, fluid under pressure is limited in its action to an annular circumferential area adjacent to the circumferential margins of the end thrust plates.

In this embodiment it may be desirable to provide each thrust plate 55' with a recess 76 in its inner annular edge face for mounting an O-ring 77 to provide a seal against the shaft 29'. It will be apparent that such a seal will 6 prevent leakage of fluid from the pump assembly along the shaft 29.

It should be noted that the pump assembly 28 is mounted within chamber 27 with substantial space between end faces thereof and the housing end plates and as long as bore 61 is open and unobstructed the pump assembly is in fluid under pressure and is out of contact with the housing end plates.

It will be readily understood by those skilled in the art that the examples of a rotary pump construction described above provide a novel construction of end sealing means for a gear pump and that such sealing means becomes more effective as the pressure is increased in the pump because of the pressure-responsive characteristics of the end thrust plates to such pressure.

It is understood that various modifications and changes in the arrangement of the rotors and bearing sleeve means and end thrust plates may be made which come within the spirit of this invention and all such modifications and changes coming within the scope of the appended claims are embraced thereby.

I claim:

1. In a rotary pump, the combination of: a housing provided with an internal chamber and inlet and outlet ports to said chamber; stationary sleeve bearing means within the chamber providing an internal, cylindrical bearing surface and contiguous annular bearing edge faces, said bearing means being provided with inlet and outlet slots in communication with respective inlet and outlet ports; a shaft mounted in the housing and extending through said chamber; the axis of said shaft being eccentric to said cylindrical bearing surface; an inner rotor carried by said shaft and provided with external teeth; an outer rotor mounted in said bearing means and provided with internal teeth to mesh with the teeth on said inner rotor, said outer rotor being provided with openings between said teeth for communication with said slots in said bearing means; thrust plates slidably mounted on said shaft for axial movement and extending over and in contact with end faces of said inner and outer rotors and having edge faces, said edge faces and said end faces lying in parallel planes; said rotors and said thrust plates being rotatable in the same direction and said thrust plates being selectively rotatable with either rotor; and passageway means for pressure fluid extending between said outlet port and outboard faces of said thrust plates.

2. A rotary pump as claimed in claim 1 wherein said passageway means extends through said bearing means.

3. A rotary pump as stated in claim 1 including end plates on said housing; and annular sealing means carried by said end plates for sealing engagement with outboard faces of said thrust plates.

4. In a rotary pump, the combination of: a housing provided with an internal chamber and inlet and outlet ports thereto; a bearing sleeve mounted in said chamber and providing an internal, cylindrical bearing surface having slots therein; a shaft extending into the chamber in eccentric relation to said cylindrical surface and mounted for rotation in said housing; relatively rotatable intermeshed inner and outer rotors carried by the shaft and sleeve respectively; said outer rotor being provided with openings for communication with said slots in said bearing sleeve, the width of said rotors and bearing sleeve being substantially equal; and sealing means slidably mounted for axial movement on said shaft at each end of said rotors and bearing sleeve for optionally self selecting rotation with either rotor in the same direction as said rotors and sealingly engaging said rotors.

5. In a rotary pump, the combination of: a housing provided with an internal chamber and fixed end plates, said housing including inlet and outlet ports for the chamber; a rotor assembly within the chamber including a shaft, an inner toothed rotor carried by the shaft and an outer internally toothed rotor enmeshed with said inner rotor, bearing means mountingsaid outer rotor for rotation in said chamber, said rotor assembly-be ng spaced at eachendfrorn said end -plates; 'and pressureresponsive sealing means including thrust plates slidably V means in communication with said outlet port and space between said thrust plates and said end plates.

7. A rotary pump asstated in claim wherein sealing means are carried by'each end plate for-pressure-sealing contact with each thrust plate 8. In a rotary pump, the combination of: a housing provided with an internal chamber and end plates, said housing being provided with inlet and outlet ports to said chamber; a rotor assembly in said chamber including a shaft mounted in said housing, a bearing'sleeve carried in said chamber and provided with a cylindrical, internal surface eccentric to said shaft, rotors carried by said shaft and said bearing sleeve and relatively rotatable in the same direction, said rotors having end faces spaced from said end plates; sealing means for said rotor ass'embly including thrust plates slidably mounted on said a shaft, rotatable in the same direction as said rotors, each self. selectively rotatable with either of said rotors, and having outboard faces spaced from said end plates; and passageway means extending from and in communication with the outlet port in said housing to spaces between said thrust plates and said end plates whereby fluid under pressure urges said thrust plates in opposed pressure balanced relation inwardly against said rotor assembly.

-9. A rotary pump as claimed in claim 8 including annular sealing means carried by said end plates in sealing contact with outboard faces of said thrust plates.

10. In a rotary pumpas claimed'in claim 9 wherein said passageway means communicates with space between said end plates and said thrust plates radially outwardly of said annular sealing means. i

11. In combination with a housing provided with a chamber having end faces and a cylindrical internal sur face, and inlet and outlet ports for the chamber; the provision ofzja unitary rotor assembly comprising a shaft; an inner externally toothed rotor fixed to the shaft for rotation therewith; 'an outer rotor having internal teeth meshing with the teeth ,of said inner rotor; and a sleeve bearing encircling the outer rotor and provided with openings for communication with the inlet and the outlet ports, the edge, faces of the rotors and sleeve bearing 8 lyingin parallel planes; n'd'thrustplates carried by the shaft in axial 'slidablere tion therewith and on opposite sidesofthe rotors, said t-hrust plates being concentric with'said-shaft and extending frorn' the shaft over the edge faces of the 'rotors; m'eans holding said thrust plates against axial movement away from said rotors whereby said inner and outer rotors and bearing sleeve are heldin "assembly as a unit for'insertion into said chamber. 7 I V 7 7 2- 12. In; a combination as stated in claim 11 wherein each thrust plate is optionally self selectively rotatable with one of the rotors 13. Ina pressure fluid balanced rotary pump including a pump chamber provided with end walls and an internal'cylindrical surface'havin'g inlet and outlet-ports through said surface, the provision of: a rotor assembly adapted to be assembled as a'unit arid comprising a shaft having end portions for mounting in said walls of'said housing; an inner rotor fixed to said shaft for rotation, an outer rotor having internal teeth engaged with said .inner rotor; a bearing sleeve provided with an external cylindrical surface corresponding to 'and adapted to be receivable within said internal cylindrical surface of said chamber. The inner surface of'saidsleeve bearing being eccentric in relation to its outer cylindrical surface and receiving therewithin saidjouter rotor; said end faces of saidrotors and said sleeve bearing lying invirtually parallel spaced common planes; and a pair of thrust plates carried by said shaft, each thrust plate being circular and extending radially outwardly from said shaft to cover said inner and outer. rotor end faces, said thrust platesbeing'held'in assembly with said'rotors and sleeve bearing, said thrust plates being spaced from the end wall of said chamber when assembled therein whereby pressure fluid introduced between said thrust plate and said end walls uniformly dynamically balances pressure exerted by said thrust plates against said rotors and whereby each thrust plate is selectively rotatable with one of the rotors.

587,684 Great Britain May 2, '1947 

